<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            /* 弹性布局 */
            display: flex;
            /* 弹性换行 */
            flex-wrap: wrap;

            /* 行对齐 对单行弹性盒子不生效*/
            /* align-content: start; */
            /* align-content: center; */
            /* align-content: end; */
            /* align-content: space-between; */
            /* align-content:space-around; */
            align-content: space-evenly;
            
            justify-content: space-between;
            height: 300px;
            border: 1px solid red;
        }
        .item{
            width: 200px;
            height: 100px;
            background-color: pink;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="item">1</div>
        <div class="item">2</div>
        <div class="item">3</div>
        <div class="item">4</div>
        <div class="item">5</div>
        <div class="item">6</div>
        <div class="item">7</div>
        <div class="item">8</div>
        <div class="item">9</div>
        <div class="item">10</div>    
        <div class="item">11</div>
        <div class="item">12</div>
       
    </div>
</body>
</html>